On the complexity of the containment problem for conjunctive queries with built-in predicates

Kolaitis, Phokion G.; Thakur, M.N.

doi:10.1145/275487.275510

Cited by 34 publications

(14 citation statements)

References 19 publications

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“…For example, [11] and [29] studied the conjunctive select-projectjoin queries and union thereof; [15] and [26] discussed the aggregate queries; [21] studied queries with arithmetic comparison predicates; [7] investigated problems of recursive queries. We, however, need to extend these techniques to the continuous stream query context.…”

Section: Stream Query Containmentmentioning

confidence: 99%

Scalable delivery of stream query result

2009

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Continuous queries over data streams typically produce large volumes of result streams. To scale up the system, one should carefully study the problem of delivering the result streams to the end users, which, unfortunately, is often overlooked in existing systems. In this paper, we leverage Distributed Publish/Subscribe System (DPSS), a scalable data dissemination infrastructure, for efficient stream query result delivery. To take advantage of DPSS's multicast-like data dissemination architecture, one has to exploit the common contents among different result streams and maximize the sharing of their delivery. Hence, we propose to merge the user queries into a few representative queries whose results subsume those of the original ones, and disseminate the result streams of these representative queries through the DPSS. To realize this approach, we study the stream query containment theories and propose efficient query grouping and merging algorithms. The proposed approach is nonintrusive and hence can be easily implemented as a middleware to be incorporated into existing stream processing systems. A prototype is developed on top of an open-source stream processing system and results of an extensive performance study on real datasets verify the efficacy of the proposed techniques.

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Section: Stream Query Containmentmentioning

confidence: 99%

Scalable delivery of stream query result

2009

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“…Since it is known that containment of conjunctive queries with disequations is Π P 2 -complete, this yields an alternative proof for Corollary 1 in the present paper. The Π P 2 lower bound for null-containment in Theorem 3 yields also the new result that containment of conjunctive queries with disequations is already Π P 2 -hard if all disequations are of the form x = c with a single constant c, which complements the lower bounds in [9,18].…”

Section: Resultsmentioning

confidence: 58%

Containment of Conjunctive Queries over Databases with Null Values

Farré

Nutt

Teniente

et al. 2006

Lecture Notes in Computer Science

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Abstract. We study containment of conjunctive queries that are evaluated over databases that may contain tuples with null values. We assume the semantics of SQL for single block queries with a SELECT DISTINCT clause. This problem ("null containment" for short) is different from containment over databases without null values and sometimes more difficult. We show that null-containment for boolean conjunctive queries is NPcomplete while it is Π P 2 -complete for queries with distinguished variables. However, if no relation symbol is allowed to appear more than twice, then null-containment is polynomial, as it is for databases without nulls. If we add a unary test predicate IS NULL, as it is available in SQL, then containment becomes Π P 2 -hard for boolean queries, while it remains in Π P 2 for arbitrary queries.

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“…Though the problem is easier if each relation symbol appears at most twice in Q1, the problem is still shown to be co-NP-complete [15]. Restriction on query-width does not make the problem easier in the presence of inequalities.…”

Section: Related Workmentioning

confidence: 99%

On the efficiency of checking perfect privacy

Machanavajjhala

Gehrke

2006

Proceedings of the Twenty-Fifth ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems

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Privacy-preserving query-answering systems answer queries while provably guaranteeing that sensitive information is kept secret. One very attractive notion of privacy is perfect privacy -a secret is expressed through a query QS, and a query QV is answered only if it discloses no information about the secret query QS. However, if QS and QV are arbitrary conjunctive queries, the problem of checking whether QV discloses any information about QS is known to be Π p 2 -complete. In this paper, we show that for large interesting subclasses of conjunctive queries enforcing perfect privacy is tractable. Instead of giving different arguments for query classes of varying complexity, we make a connection between perfect privacy and the problem of checking query containment. We then use this connection to relate the complexity of enforcing perfect privacy to the complexity of query containment.

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On the complexity of the containment problem for conjunctive queries with built-in predicates

Cited by 34 publications

References 19 publications

Scalable delivery of stream query result

Scalable delivery of stream query result

Containment of Conjunctive Queries over Databases with Null Values

On the efficiency of checking perfect privacy

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